1. Field of the Invention
The invention relates to a photomask and a semiconductor structure.
2. Description of Related Art
As the critical dimension (CD) of semiconductor structures continues to be reduced, the requirement on the resolution of photolithography also becomes higher. Generally speaking, there is usually a high pattern density device region (e.g. memory cell region or array region) and a low pattern density device region (e.g. peripheral region). In a boundary region of the high pattern density device region, which is close to the low pattern density device region, holes in uneven sizes and even blind hole defects of the semiconductor structure are commonly produced due to a significant difference in pattern density. As a result, the product reliability is reduced. Thus, how to improve the uniformity of critical dimension in the boundary region and reduce the defects and blind holes in the semiconductor structure, thereby improving the product reliability, has become an important issue.